79 research outputs found
Higgs inflation: consistency and generalisations
We analyse the self-consistency of inflation in the Standard Model, where the
Higgs field has a large non-minimal coupling to gravity. We determine the
domain of energies in which this model represents a valid effective field
theory as a function of the background Higgs field. This domain is bounded
above by the cutoff scale which is found to be higher than the relevant
dynamical scales throughout the whole history of the Universe, including the
inflationary epoch and reheating. We present a systematic scheme to take into
account quantum loop corrections to the inflationary calculations within the
framework of effective field theory. We discuss the additional assumptions that
must be satisfied by the ultra-violet completion of the theory to allow
connection between the parameters of the inflationary effective theory and
those describing the low-energy physics relevant for the collider experiments.
A class of generalisations of inflationary theories with similar properties is
constructed.Comment: 25 pages, 1 figur
Standard Model Higgs boson mass from inflation: two loop analysis
We extend the analysis of \cite{Bezrukov:2008ej} of the Standard Model Higgs
inflation accounting for two-loop radiative corrections to the effective
potential. As was expected, higher loop effects result in some modification of
the interval for allowed Higgs masses m_min<m_H<m_max, which somewhat exceeds
the region in which the Standard Model can be considered as a viable effective
field theory all the way up to the Planck scale. The dependence of the index
n_s of scalar perturbations on the Higgs mass is computed in two different
renormalization procedures, associated with the Einstein (I) and Jordan (II)
frames. In the procedure I the predictions of the spectral index of scalar
fluctuations and of the tensor-to-scalar ratio practically do not depend on the
Higgs mass within the admitted region and are equal to n_s=0.97 and r=0.0034
respectively. In the procedure II the index n_s acquires the visible dependence
on the Higgs mass and and goes out of the admitted interval at m_H below m_min.
We compare our findings with the results of \cite{DeSimone:2008ei}.Comment: 24 paged, 9 figures. Journal version (typos fixed, expanded
discussions
On initial conditions for the Hot Big Bang
We analyse the process of reheating the Universe in the electroweak theory
where the Higgs field plays a role of the inflaton. We estimate the maximal
temperature of the Universe and fix the initial conditions for
radiation-dominated phase of the Universe expansion in the framework of the
Standard Model (SM) and of the nuMSM -- the minimal extension of the SM by
three right-handed singlet fermions. We show that the inflationary epoch is
followed by a matter dominated stage related to the Higgs field oscillations.
We investigate the energy transfer from Higgs-inflaton to the SM particles and
show that the radiation dominated phase of the Universe expansion starts at
temperature T_r~(3-15)*10^{13} GeV, where the upper bound depends on the Higgs
boson mass. We estimate the production rate of singlet fermions at preheating
and find that their concentrations at T_r are negligibly small. This suggests
that the sterile neutrino Dark Matter (DM) production and baryogenesis in the
nuMSM with Higgs-driven inflation are low energy phenomena, having nothing to
do with inflation. We study then a modification of the nuMSM, adding to its
Lagrangian higher dimensional operators suppressed by the Planck scale. The
role of these operators in Higgs-driven inflation is clarified. We find that
these operators do not contribute to the production of Warm Dark Matter (WDM)
and to baryogenesis. We also demonstrate that the sterile neutrino with mass
exceeding 100 keV (a Cold Dark Matter (CDM) candidate) can be created during
the reheating stage of the Universe in necessary amounts. We argue that the
mass of DM sterile neutrino should not exceed few MeV in order not to overclose
the Universe.Comment: 41 pages, 5 figures. Journal version accepted in JCA
nuMSM and its experimental tests
MSM is a minimal renormalizable extension of the Standard Model by right
handed neutrinos. This model explains the neutrino oscillations and provides a
candidate for the Dark Matter and a mechanism of baryon number generation in
the Early Universe. We discuss here existing constraints on the model and
possible consequences for astrophysical and laboratory experiments.Comment: 4 pages. To appear in the proceedings of International Europhysics
Conference on High Energy Physics (EPS-HEP2007), Manchester, England, 19-25
Jul 200
Can an odd number of fermions be created due to chiral anomaly?
We describe a possibility of creation of an odd number of fractionally
charged fermions in 1+1 dimensional Abelian Higgs model. We point out that for
1+1 dimensions this process does not violate any symmetries of the theory, nor
makes it mathematically inconsistent. We construct the proper definition of the
fermionic determinant in this model and underline its non-trivial features that
are of importance for realistic 3+1 dimensional models with fermion number
violation.Comment: 12 pages revtex, 2 figure
Some constraints on the Yukawa parameters in the neutrino modification of the Standard Model (nuMSM) and CP-violation
The equations connecting elements of the Yukawa matrix to elements of the
active neutrino mass matrix in the \nu MSM theory (an extension of the Standard
Model by a singlet of three right-handed neutrinos) was analyzed, and explicit
relations for the ratio of the Yukawa matrix elements through elements of the
active neutrino mass matrix were obtained. This relation can be used for
getting more accurate constraints on the model parameters. Particularly, with
the help of the obtained results we investigated CP-violating phase in the \nu
MSM theory. We demonstrate that even in the case when elements of the active
neutrino mass matrix are real the baryon asymmetry can be generated also.Comment: 14 pages, 2 figures, many clarifications and references adde
Inflation by non-minimal coupling
Inflationary scenarios based on simple non-minimal coupling and its
generalizations are studied. Generalizing the form of non-minimal coupling to
"K(phi)R" with an arbitrary function K(phi), we show that the flat potential
still is obtainable when V(phi)/K^2(phi) is asymptotically constant. Very
interestingly, if the ratio of the dimensionless self-coupling constant of the
inflaton field and the non-minimal coupling constant is small the cosmological
observables for general monomial cases are in good agreement with recent
observational data.Comment: 9 pages, 1 figur
Mixing of Active and Sterile Neutrinos
We investigate mixing of neutrinos in the MSM (neutrino Minimal Standard
Model), which is the MSM extended by three right-handed neutrinos. Especially,
we study elements of the mixing matrix between three
left-handed neutrinos () and two sterile
neutrinos () which are responsible to the seesaw mechanism
generating the suppressed masses of active neutrinos as well as the generation
of the baryon asymmetry of the universe (BAU). It is shown that
can be suppressed by many orders of magnitude compared with
and , when the Chooz angle is large in the
normal hierarchy of active neutrino masses. We then discuss the neutrinoless
double beta decay in this framework by taking into account the contributions
not only from active neutrinos but also from all the three sterile neutrinos.
It is shown that and give substantial, destructive contributions
when their masses are smaller than a few 100 MeV, and as a results receive no stringent constraint from the current bounds on such decay.
Finally, we discuss the impacts of the obtained results on the direct searches
of in meson decays for the case when are lighter than pion
mass. We show that there exists the allowed region for with such
small masses in the normal hierarchy case even if the current bound on the
lifetimes of from the big bang nucleosynthesis is imposed. It is also
pointed out that the direct search by using and might miss such since the branching ratios can be
extremely small due to the cancellation in , but the search by
can cover the whole allowed region by improving the
measurement of the branching ratio by a factor of 5.Comment: 30 pages, 32 figure
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